In general, in-vehicle knob switches, which are called stalk switches, are provided in the vicinity of a steering column of a vehicle in order to control the operation of a wiper or a headlight. The in-vehicle knob switch includes a tubular housing that is tiltably supported by the steering column, a circuit board that is fixed to a holder in the housing, a rotating body that includes an operating ring portion and is rotatably mounted to an outer circumferential surface of the housing, and an operating key that is exposed from the outer circumferential surface of the housing. The circuit board has electric parts, such as a push switch that is operated by the push of the operating key and a rotary volume that is operated by the rotation of the operating ring portion, mounted thereon. A user tilts the housing, pushes the operating key provided on the outer circumferential surface of the housing, or rotates the operating ring portion to turn on or off the wiper, control the speed and intermittent operation of the wiper, or turn on or off the headlight or control the beam direction of the headlight.
An in-vehicle knob switch having the following structure has been proposed: a push switch is mounted on one surface of a circuit board, and a rotary volume (a rotation detecting electric part) is mounted on the other surface of the circuit board; an operating key is disposed at a position facing a stem of the push switch; and two kinds of gears are provided to transmit the rotation of an operating ring portion to the rotary volume (for example, refer to U.S. Pat. No. 5,905,237, which corresponds to JP-A-10-269898). The axes of the two kinds of gears are orthogonal to each other. A first gear is integrally formed with the operating ring portion, and a shaft of a second gear engaged with the first gear is splined to a rotating shaft of the rotary volume. In this way, when the user rotates the operating ring portion, the rotating shaft of the rotary volume is rotated through the first and second gears, and a signal corresponding to the rotation of the ring portion is output from the rotary volume. When the user pushes the operating key, the stem of the push switch is pushed, and on/off signals corresponding to the push of the operating key are output from the push switch.
However, in this kind of in-vehicle knob switch, as in the related art, when the rotation of the operating ring portion is transmitted to the rotation detecting electric part through the two gears, the structure of the rotation transmitting mechanism becomes complicated, which makes it difficult to manufacture the rotation transmitting mechanism at a low cost.
Therefore, the inventors have proposed a rotation transmitting mechanism in which, in order to omit the two kinds of gears, a tubular driving portion having a spiral hole formed in a circumferential wall thereof is integrally formed with an operating ring portion, and a slider engaged with the spiral hole reciprocates in a straight line along a circuit board with the forward or backward rotation of the operating ring portion. That is, a slide operating type electric part having a slider that can reciprocate in a straight line is used as the rotation detecting electric part, and the slider is engaged with the spiral hole of the tubular driving portion that is integrally rotated with the operating ring portion. The rotary power of the tubular driving portion is converted into the rectilinear motion of the slider by the engaging portion. According to this structure, it is not necessary to provide the two kinds of gears between the operating ring portion and the rotation detecting electric part. As a result, it is possible to reduce manufacturing costs.
In the in-vehicle knob switch having the rotation transmitting mechanism in which the slider of the rotation detecting electric part is directly driven by the tubular driving portion integrally formed with the operating ring portion, it is necessary to provide the tubular driving portion so as not to hinder the up and down movement of the operating key that is opposite to the push switch. It is easy to arrange the tubular driving portion between the operating ring portion and the operating key in the housing. However, when a space for the arrangement of the tubular driving portion is ensured between the operating ring portion and the operating key, a large positional deviation between the operating ring portion and the operating key occurs in the longitudinal direction of the circuit board. In this case, when the user continuously operates the operating ring portion and the operating key, the movement of fingers increases, which results in low operability. In addition, when a space for the arrangement of the tubular driving portion is ensured between the operating ring portion and the operating key, a region in which the rotation detecting electric part is mounted and a region in which the push switch is mounted on both surfaces of the circuit board deviate from each other in the longitudinal direction of the circuit board. As a result, the size of the circuit board increases, which makes it difficult to reduce the size of the housing. That is, the size or diameter of the tubular housing should be reduced due to the restrictions of the design. However, when there are difficulties in reducing the size of the circuit board in the housing due to the mounting space, it is difficult to reduce the size of the housing. The related art has not solved these problems.